The present invention relates to cruise control systems for motor vehicles.
Cruise control systems currently fitted on motor vehicles, once engaged by the driver, would maintain the vehicle at a constant speed without the driver having to take action. Such systems operate conventionally through the vehicle throttle only.
Cruise control systems of this type are beneficial on open roads with low traffic flows. However, on more congested roads where the equipped vehicle may catch up with slow moving vehicles or passing vehicles may pull in front of the equipped vehicle at an unsafe distance, the driver must frequently disengage the cruise control system, so that he may adjust the speed of the equipped vehicle to maintain a safe distance from the vehicles in front.
It has been proposed to fit a forward looking distance sensor at the front of the equipped vehicle, so that by using brake and throttle interaction, the cruise control system may be used to maintain a safe distance from a target vehicle in front of the equipped vehicle. Such systems should be capable of maintaining a safe distance between vehicles and even if the target vehicle brakes moderately, it should be possible to maintain a safe distance without excessive braking of the equipped vehicle. If the system assesses that a braking effort in excess of for example 0.3 g is required, the system will alert the driver and it will be up to the driver to apply a greater braking effort if he considers it necessary. This will happen if a vehicle pulls in front of the equipped vehicle, thus taking the place of the target vehicle but at a much closer distance. In such circumstances, it will appear to the cruise control system that the target vehicle has slowed to such an extent that emergency braking is required. However, it is probable in such circumstances, that the vehicle pulling in is travelling faster than or at equal speed to the equipped vehicle and that a safe driving distance can be achieved with only moderate deceleration.